Step 1

In a saucepan, combine sugar, cornstarch, butter, lemon rind, lemon juice and egg yolks. Whisk together.

Step 2

Add milk. Whisk again. Turn heat to medium and cook until thickened, stirring constantly to prevent burning.

Step 3

Remove pan from heat when mixture thickens. Let cool and fold in sour cream.

Step 4

Pour into baked pie shell. Let chill for 3 hours in fridge.

Step 5

Whip cream and powdered sugar together until thick.

Step 6

Serve with whipped cream and garnish with lemon slices just before serving.